Testing backplanes that drive current rather than voltage presents a challenging problem. At present, there is a need for an acceptable solution for measuring current actuated display (CAD) backplanes prior to application of a display medium to such backplanes.
Typically, backplanes are fabricated with test structures that allow general parametric measurement of the substrate, without any detail pertaining to individual display elements (pixels, data lines, gate lines, ground busses, power busses). In this regard, with satisfactory substrate parameters, displays are then assembled with a medium (e.g. an organic light emitting diode (OLED)). The finished displays may then be imaged with a camera to measure uniformity, area defects, line defects, and pixel defects. However, with these types of testing systems, problems cannot be detected until after the display is completed.
A variety of testers for AMLCD backplanes are known. However, none are known for OLED backplanes.
Also, U.S. Pat. No. 7,295,030 teaches the use of a vacuum tip to capture current without contact. However, a convenient visual system is not disclosed.